This UCLA Symposium will address the molecular biology of the cardiovascular system. While the cause of essential hypertension is still unknown, molecular approaches promise to advance understanding of critical mechanisms regulating the arterial pressure (AP) in health and disease. The development of molecular probes now permits a molecular analysis of three peptide hormones/modulators involved in AP regulation: the renin- angiotensin system, atrial natriuretic factor, and arginine vasopressin. Insights into expression of the genes generating the prohormones and their processing enzymes, processing of messages and genes, control of tissue-specific expression (particularly in brain), molecular biology of receptors and second messenger systems and their role in gene expression in target tissues will be discussed, particularly in relationship to hypertensive disease. New insights into the regulation of the autonomic nervous system by specific neural networks has reaffirmed the importance of the brain in blood pressure control. The general problems of the molecular neurobiology of neurotransmitter systems in central and peripheral neural systems governing AP, in particular those containing catecholamines, is ripe for review. Finally, analysis of the molecular mechanisms by which nerves control the growth and molecular integrity of blood vessels and myocardium is relevant for unravelling some of the pathophysiological consequences of chronically elevated AP.